Self-lit display panel

ABSTRACT

A self-lit display panel includes a photonic integrated circuit payer including an array of waveguides and an array of out-couplers for out-coupling portions of the illuminating light through pixels of the panel. The self-lit display panel may include a transparent electronic circuitry layer backlit by the photonic integrated circuit layer; the two layers may be on a same substrate or on opposed substrates defining a cell filled with an electro-active material. The configuration allows for chief ray engineering, zonal illuminating, and separate illumination with red, green, and blue illuminating light.

REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. applicationSer. No. 17/741,404 filed May 10, 2022, which claims priority from U.S.Provisional Application No. 63/288,342 filed on Dec. 10, 2021 andentitled “Backplane-Embedded Photonic Integrated Circuit”, and U.S.Provisional Application No. 63/288,920 filed on Dec. 13, 2021 andentitled “Backplane-Embedded Photonic Integrated Circuit”, all of whichbeing incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to electro-optical devices, and inparticular to visual display panels and their methods of manufacturing.

BACKGROUND

Visual displays provide information to viewer(s) including still images,video, data, etc. Visual displays have applications in diverse fieldsincluding entertainment, education, engineering, science, professionaltraining, advertising, to name just a few examples. Some visual displayssuch as TV sets display images to several users, and some visual displaysystems such s near-eye displays (NEDs) are intended for individualusers.

An artificial reality system generally includes an NED, e.g. a headsetor a pair of glasses, configured to present content to a user. Thenear-eye display may display virtual objects or combine images of realobjects with virtual objects, as in virtual reality (VR), augmentedreality (AR), or mixed reality (MR) applications. For example, in an ARsystem, a user may view images of virtual objects (e.g.computer-generated images or CGIs) superimposed with the surroundingenvironment by seeing through a “combiner” component. The combiner of awearable display is typically transparent to external light but includessome light routing optic to direct the display light into the user'sfield of view.

Because a display of HMD or NED is usually worn on the head of a user, alarge, bulky, unbalanced, and heavy display device with a heavy batterywould be cumbersome and uncomfortable for the user to wear.Consequently, head-mounted display devices can benefit from a compactand efficient configuration, including efficient light sources andilluminators providing illumination of a display panel, high-throughputcollimators and other optical elements in the image forming train.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments will now be described in conjunction with thedrawings, in which:

FIG. 1A is a side cross-sectional view of a self-lit display panelincluding a photonic integrated circuit layer formed over an electroniccircuitry layer on a silicon substrate;

FIG. 1B is a three-dimensional partial view of the illuminatingwaveguides and vias region of the self-lit display panel of FIG. 1A;

FIG. 2 is a side cross-sectional view of a self-lit display panelincluding a photonic integrated circuit layer supported by an electroniccircuitry layer on a transparent substrate;

FIG. 3 is a side cross-sectional view of a self-lit display panelincluding an electronic circuitry layer supported by a photonicintegrated circuit layer on a substrate;

FIG. 4 is a side cross-sectional view of a self-lit display panelincluding photonic integrated circuit and electronic circuitry layers onopposed substrates;

FIG. 5 is a flow chart of a method of manufacture of an electroniccircuitry layer on a transparent substrate, and of a self-lit displaybased thereon;

FIGS. 6A and 6B are schematic views of near-eye displays based on aself-lit display panel of FIGS. 1A, 1B, and FIGS. 2-4 without (FIG. 6A)and with (FIG. 6B) chief ray engineering;

FIGS. 7A to 7D are side cross-sectional views of various embodiments ofgrating out-couplers of a photonic integrated circuit of a self-litdisplay panel of this disclosure;

FIG. 8A is a top view of a slanted grating embodiment of out-couplers ofa photonic integrated circuit of a self-lit display panel of thisdisclosure;

FIG. 8B is a side cross-sectional view of a grating out-coupler with ananostructure-based chief ray angle control, usable in the photonicintegrated circuit of a self-lit display panel of this disclosure;

FIG. 8C is a top view of a nanoantenna embodiment of out-couplers of aphotonic integrated circuit of the self-lit display panel of a self-litdisplay panel of this disclosure;

FIGS. 9A to 9C are schematic views of color illumination configurationsfor a self-lit display panel of this disclosure;

FIG. 10 is a top schematic view of a photonic integrated circuitconfigured for zonal illumination of a display panel of this disclosure;

FIG. 11 is a view of near-eye display of this disclosure having a formfactor of a pair of eyeglasses; and

FIG. 12 is a three-dimensional view of a head-mounted display (HMD) ofthis disclosure.

DETAILED DESCRIPTION

While the present teachings are described in conjunction with variousembodiments and examples, it is not intended that the present teachingsbe limited to such embodiments. On the contrary, the present teachingsencompass various alternatives and equivalents, as will be appreciatedby those of skill in the art. All statements herein reciting principles,aspects, and embodiments of this disclosure, as well as specificexamples thereof, are intended to encompass both structural andfunctional equivalents thereof. Additionally, it is intended that suchequivalents include both currently known equivalents as well asequivalents developed in the future, i.e., any elements developed thatperform the same function, regardless of structure.

As used herein, the terms “first”, “second”, and so forth are notintended to imply sequential ordering, but rather are intended todistinguish one element from another, unless explicitly stated.Similarly, sequential ordering of method steps does not imply asequential order of their execution, unless explicitly stated. In FIGS.1A, 1B, and FIGS. 2-4 , similar number refer to similar elements.

Resolution, power consumption, and form factor are important performancefactors in AR displays. MicroLED displays (μLED) have an advantage ofhigh brightness, although efficiency of such displays quickly goes downwith pixel size reduction. Furthermore, due to the different materialsrequired for red and blue/green LEDs, it may be challenging to achieve asingle panel full-color μLED display. As a result, three separate μLEDprojectors for color display applications may need to be used, whichresults in tripling of the light engine size and weight. Anotherapproach is to use a 2D scanned light beam produced by lasers orsuperluminescent light-emitting diodes (SLEDs) impinging onto amicroelectromechanical system (MEMS) scanning reflector. However, driverand graphics processing controller are quite complicated and energyconsuming, and overall achievable resolution may be limited by ascanning mirror size.

Miniature display panels based on nematic or ferroelectric liquidcrystals on silicon (LCoS and FLCoS respectively) provide an alternativesolution for a light engine usable in near-eye displays such as virtualreality or augmented reality displays. With the advancement of novelferroelectric liquid crystal materials, pixel sizes smaller than 1.5 um(down to 350 nm) become possible. However, unlike emissive displays,(F)LCoS displays require additional illumination optics such aspolarization beam splitters, which add size and weight to the system.

The latter limitation of (F)LCoS display panels may be overcome byintegrating the illumination circuitry directly onto the (F)LCoSsubstrate. A photonic integrated circuit (PIC) layer may be provided onthe integrated circuitry layer of a complementary metal oxidesemiconductor (CMOS) chip, providing a self-lit display panel.Furthermore, the PLC technology may be adapted to provide a so-calledchief ray engineering capability. The PLC technology may be used todirect chief rays of light beams emitted by each pixel towards a commoncollimating element, resulting in a significant reduction of overallsize and/or vignetting losses, and an increase of overall wall plugefficiency of the display apparatus. Furthermore, the PIC technology canprovide features such as zonal illumination of the display panel forhigher perceived contrast and power savings. Yes furthermore, CMOStechnology may be adapted to provide circuitry with substantiallytransparent pixel areas, providing a greater variety of CMOS PLCillumination configurations and opening a path to transparent ortranslucent self-lit displays.

In accordance with the present disclosure, there is provided a self-litdisplay panel comprising a first substrate, a photonic integratedcircuit (PIC) layer supported by the first substrate, the PIC layercomprising an array of waveguides for guiding illuminating light, anelectronic circuitry layer supported by the PIC layer, and a pixelatedelectrode layer comprising an array of pixel electrodes. The electroniccircuitry layer is configured for applying electrical signals to thearray of pixel electrodes. The PIC layer comprises an array ofout-couplers coupled to the array of waveguides for out-couplingportions of the illuminating light through the electronic circuitrylayer and through the array of pixel electrodes.

The self-lit display panel may further include a second substrateopposite the first substrate, a backplane electrode layer supported bythe second substrate, the pixelated and backplane electrode layersdefining a cell, and an electroactive layer in the cell. In operation,the illuminating light portions may propagate in sequence through theelectronic circuitry layer, the pixel electrodes, the electroactivelayer, the backplane electrode, and the second substrate. Theelectroactive layer may include liquid crystals.

In some embodiments, the array of out-couplers comprises gratings formedin the array of waveguides. The gratings may be slanted to provide achief ray angle of the portions of the illuminating light spatiallyvarying from one pixel electrode to another. In some embodiments, thearray of out-couplers comprises an array of nanostructures to provide achief ray angle of the portions of the illuminating light spatiallyvarying from one pixel electrode to another.

In embodiments where the illuminating light comprises a plurality ofcolor channels, each waveguide of the array of waveguides may beconfigured to convey each color channel of the plurality of colorchannels. Each out-coupler of the array of out-couplers may beconfigured to out-couple each color channel of the plurality of colorchannels at a substantially same chief ray angle. In some embodiments,the array of waveguides comprises a plurality of sub-arrays, and eachsub-array may be configured to carry a particular color channel of theplurality of color channels of the illuminating light.

In accordance with the present disclosure, there is provided a self-litdisplay panel comprising: first and second opposed substrates; aphotonic integrated circuit (PIC) layer supported by the firstsubstrate, the PIC layer comprising an array of waveguides for guidingilluminating light; a backplane electrode layer supported by the PIClayer; an electronic circuitry layer supported by the second substrate;a pixelated electrode layer comprising an array of pixel electrodes,wherein the electronic circuitry layer is configured for applyingelectrical signals to the array of pixel electrodes, the pixelated andbackplane electrode layers defining a cell; and an electroactive layerin the cell. The PIC layer may include an array of out-couplers coupledto the array of waveguides for out-coupling portions of the illuminatinglight through the backplane electrode layer, the electroactive layer,and the array of pixel electrodes. The electroactive layer may includeliquid crystals.

In embodiments where the array of out-couplers comprises gratings formedin the array of waveguides, the gratings may be slanted to provide achief ray angle of the portions of the illuminating light spatiallyvarying from one pixel electrode to another. In some embodiments, thearray of out-couplers comprises an array of nanostructures to provide achief ray angle of the portions of the illuminating light spatiallyvarying from one pixel electrode to another.

In embodiments where the illuminating light comprises a plurality ofcolor channels, each waveguide of the array of waveguides may beconfigured to convey each color channel of the plurality of colorchannels. Each out-coupler of the array of out-couplers may beconfigured to out-couple each color channel of the plurality of colorchannels at a substantially same chief ray angle.

In embodiments where the array of waveguides comprises a plurality ofsub-arrays, each sub-array may be configured to carry a particular colorchannel of the plurality of color channels of the illuminating light.Each sub-array may be coupled to a beamsplitter for illuminating aparticular geometrical area of the array of pixel electrodes.

In accordance with the present disclosure, there is further provided amethod of manufacturing a self-lit display panel. The method comprisesforming an electronic circuitry layer on a sacrificial substrate, theelectronic circuitry layer comprising a pixelated electrode layercomprising an array of pixel electrodes; bonding a first substrate tothe electronic circuitry layer; removing the sacrificial substrate;providing a photonic integrated circuit (PIC) layer comprising an arrayof waveguides for guiding illuminating light and an array ofout-couplers coupled to the array of waveguides for out-couplingportions of the illuminating light; forming a cell by providing a secondsubstrate in a fixed-apart relationship with the first substrate, thesecond substrate supporting a backplane electrode layer, wherein thepixelated electrode layer faces the cell, and wherein in operation, theilluminating light portions propagate through the array of pixelelectrodes; and filling the cell with an electro-active material.

The PIC layer may be formed on the first substrate and faces the cellwhen the cell is formed. The electronic circuitry layer may be disposedbetween the PIC layer and the electro-active material. The PIC layer maybe formed on the second substrate to face the cell when the cell isformed.

Referring now to FIG. 1A, a self-lit display panel 100 includes anelectronic circuitry layer 102 supported by a first substrate 104, forexample a CMOS circuitry layer formed on a silicon substrate. Theelectronic circuitry layer 102 may include electronic gates 103 forindependently controlling individual pixels of the display panel 100.The pixels of the display panel 100 are defined by a pixelated electrodelayer 106 including an array of pixel electrodes 107.

A photonic integrated circuit (PIC) layer 108 may be formed on, disposedon, and/or supported by, the electronic circuitry layer 102. The PIClayer 108 may include an array of waveguides 109, e.g. singlemode orfew-mode ridge-type waveguides running under the array of pixelelectrodes 107 and configured for guiding illuminating light 110 emittedby an optional semiconductor light source 112 optically coupled to thewaveguides 109. Herein, the term “few-mode waveguide” refers towaveguides supporting up to 12 lateral modes of propagation. Thesemiconductor light source 112 may be e.g. a superluminescentlight-emitting diode, a laser diode, or an array of such diodes. The PIClayer 108 supports the pixelated electrode layer 106.

The PIC layer 108 may include an array of out-couplers 111, e.g. gratingout-couplers optically coupled to the array of waveguides 109 forout-coupling portions 110A of the illuminating light 110 through thearray of pixel electrodes 107, providing the display panel 100 with aself-lighting capability. Herein, the term “self-lighting” or“self-lit”means that the pixels of the display panel are illuminatedfrom inside by an inside illuminating or light-guiding structure, asopposed to a reflective or transmissive display panel requiring anexternal light source shining light on the panel from outside tooperate. The out-couplers 111 are registered w.r.t. the pixel electrodes107, e.g. one out-coupler 111 may be disposed directly under one pixelelectrode 107.

In the embodiment shown in FIG. 1A, the display panel 100 includes asecond substrate 120 disposed opposite the first substrate 104, and abackplane electrode layer 122 supported by the second substrate 120. Thepixelated 106 and backplane 118 electrode layers define a cell 116,typically a plano-parallel cell from 1 to 9 micrometers thick. Anelectroactive layer 124, e.g. a layer of a nematic or ferroelectricliquid crystal fluid, may fill the cell 116. The electroactive layer 124is responsive to an electric field applied by the pixelated 106 andbackplane 118 electrode layers. Herein, the term “responsive to anelectric field” means that the electroactive layer 124 changes itsproperty that influences an optical property of the portions 110A of theilluminating light 110, such as polarization state, by application ofthe electric field.

The second substrate 120 is transparent to the portions 110A of theilluminating light 110. In the illustrated embodiment, the PIC layer 108is disposed between the electronic circuitry layer 102 and the pixelatedelectrode layer 106, and electrically separates these two layers. Toelectrically couple the electronic gates 103 to the respective pixelelectrodes 107, an array of electrically conductive vias 114 may beprovided, allowing the gates 103 of the electronic circuitry layer toapply electrical signals to the respective pixel electrodes 107. As bestseen in FIG. 1B, the array of vias 114 may extend from the electroniccircuitry layer 102 through the PIC layer 108 between the waveguides 109of the array and to the array of pixel electrodes 107 at a distancelarge enough to substantially not perturb the optical function of thewaveguides 109 and out-couplers 111.

In operation, the illuminating light portions 110A out-coupled by theout-couplers 111 from the waveguides 109 propagate in sequence throughthe pixel electrodes 107, the electroactive layer 124, the backplaneelectrode layer 122, and the transparent second substrate 120. Theoptical property of the portions 110A, e.g. their polarization state,may be controlled in a spatially selective manner by applying signals tothe gates 103, which are electrically coupled to the respective pixelelectrodes 107 through the vias 114 to change local electric fieldapplied to the respective portions of the electroactive layer 124. Thespatially varying polarization state of the out-coupled illuminatinglight portions 110A may be converted into the optical power densitydistribution by a downstream polarizer, not shown for brevity. Theoptical power density distribution of the illuminating light portions110A corresponds to an image displayed by the display panel 100.

Referring to FIG. 2 , a self-lit display panel 200 is similar to theself-lit display panel 100 of FIG. 1 , and includes similar elements.The self-lit display panel 200 of FIG. 2 includes the electroniccircuitry layer 102 supported by a transparent first substrate 204, e.g.glass, sapphire, crystal, etc., the PIC layer 108 on the electroniccircuitry layer 102, the pixelated electrode layer 106 on the PIC layer108 with the vias 114 electrically coupling the pixelated electrodelayer 106 to the electronic circuitry layer 102 through the PIC layer108 as described above. The cell 116 defined by the pixelated electrode106 and the backplane 118 electrode layers is filled with theelectroactive layer 124. The second substrate 120 supports the backplaneelectrode layer 118 including the backplane electrode 122.

Opaque substrate material may be removed in areas 202 under pixelelectrodes 107 between the electronic gates 103, making the firstsubstrate 204 with the electronic circuitry layer 102 transparent toimpinging light in the areas of the pixel electrodes 107. Thetransparent substrate 204 and the transparent electronic circuitry layer102 enable the self-lit display panel 200 to be used in a variety ofapplications such as, for example and without limitation, in augmentedreality (AR) applications where the image light formed by theout-coupled portions 110A of the illuminating light 110 needs to becombined with external light from surrounding environment. A method ofmanufacturing the electronic circuitry layer 102 on the transparentsubstrate 204 will be considered further below.

Turning to FIG. 3 , a self-lit display panel 300 is similar to theself-lit display panel 200 of FIG. 2 , and includes similar elements. Inthe self-lit display panel 300 of FIG. 3 , the positions of theelectronic circuitry layer 102 and the PIC layer 108 in a layer stacksupported by the first substrate 204 are swapped, i.e. the transparentfirst substrate 204 supports the PIC layer 108, which in its turnsupports the electronic circuitry layer 102. Such a configuration doesnot need vias since the pixelated electrode layer 106 may be directlycoupled to the electronic circuitry layer 102, allowing the gates 103 ofthe electronic circuitry layer to apply electrical signals to therespective pixel electrodes 107. The overall construction is simplified,since vias manufacturing adds many steps to the manufacturing process.

In operation, the illuminating light portions 110A out-coupled from thewaveguide 109 by the array of out-couplers 111 propagate in sequencethrough the electronic circuitry layer 102 (specifically through theareas 202 transparent for the illumination light portions 110), thepixelated electrode layer 106, the electroactive layer 124, thebackplane electrode layer 118, through the second substrate 120, and outof the self-lit display panel 300. A collimator, not shown for brevity,may receive the illuminating light portions 110A and convert an image inlinear domain displayed by the self-lit display panel 300 into an imagein angular domain. Herein, the term “image in angular domain” means animage where different elements of an image in linear or spatial domain,i.e. pixels of the image displayed by the display panel, are representedby angles of corresponding rays of image light, the rays carryingoptical power levels and/or color composition corresponding tobrightness and/or color values of the image pixels.

Referring now to FIG. 4 , a self-lit display panel 400 is similar to theself-lit display panel 300 of FIG. 3 , and includes similar elements. Inthe self-lit display panel 400 of FIG. 4 , the electronic circuitrylayer 102 is moved to the other substrate; in other words, the firstsubstrate 204 supports the PIC layer 108 supporting the backplaneelectrode layer 118, while the second substrate 120 supports theelectronic circuitry layer 102, which supports the pixelated electrodelayer 106 (shown inverted in FIG. 4 ). The pixelated 106 and backplane118 electrode layers define the cell 116, with the electroactive layer124 disposed in the cell 116, as in previous embodiments.

In operation, the illuminating light portions 110A out-coupled from thewaveguide 109 by the plurality of out-couplers 111 propagate in sequencethrough the backplane electrode 122, the electroactive layer 124, thepixel electrodes 107, the electronic circuitry layer 102 (morespecifically through the transparent areas 202), and the secondtransparent substrate 120, and further to collimating/image formingoptics, not illustrated.

Turning to FIG. 5 , a method 500 of manufacturing a self-lit displaypanel of this disclosure includes forming (502) an electronic circuitrylayer on a sacrificial substrate, for example forming a CMOS electroniccircuitry layer on a silicon substrate. The electronic circuitry layermay include pixel controlling gates, connections, vias, pixelatedelectrode layer including an array of pixel electrodes, etc., as neededfor the intended display operation. The formed electronic circuitrylayer is bonded (504) to a first substrate, e.g. a glass or sapphiretransparent substrate, from the opposite side of the electroniccircuitry layer. The sacrificial substrate is then removed (506) e.g. byetching.

Opaque material from under pixelated electrodes may be cleared (508),and the resulting structure may be backfilled or planarized (510) toform transparent areas such as, for example, the areas 202 under pixelelectrodes of the self-lit display panel 200 of FIG. 2 , the self-litdisplay panel 300 of FIG. 3 , or the self-lit display panel 400 of FIG.4 . A PIC layer may be then provided (512). The PIC layer may bedisposed on the planarized electronic circuitry layer (“EC layer” inFIG. 5 ) as in, for example, the self-lit display panel 300 of FIG. 3 .The electronic circuitry layer may be placed on another substrate of thecell, as in, for example, the self-lit display panel 400 of FIG. 4 . Theformed PIC layer may include an array of waveguides for guidingilluminating light, and an array of out-couplers coupled to the array ofwaveguides for out-coupling portions of the illuminating light, asexplained above with reference to FIGS. 1-4 . A cell may be then formed(514), by providing a second substrate in a fixed-apart relationshipwith the first substrate, the second substrate supporting a backplaneelectrode layer. The cell is defined by the electrodes facing into thecell as in the display panels of FIGS. 1-4 . The cell may then be filled(516) with an electro-active material such as, for example, a nematic orferroelectric LC fluid.

In some embodiments, for example in the self-lit display panel 200 ofFIG. 2 and in the self-lit display panel 300 of FIG. 3 , the PIC layeris formed on the first substrate, facing the cell when the cell isformed. In such embodiments, the electronic circuitry layer may bedisposed between the PIC layer and the electro-active material. In someembodiments, the PIC layer may be formed on the second substrate facingthe cell when the cell is formed as in, for example, the self-litdisplay panel 400 of FIG. 4 .

The self-lit property afforded by a PIC structure with waveguides andout-coupler arrays enables directing chief rays of the individualout-coupled illuminating light portions to pre-defined locations, e.g.to a location of a collimating element such as a collimator lens,so-called chief ray engineering. Herein, the term “chief ray” refers toa ray carrying the most of the emitted light energy as compared to otherrays in a ray fan representing a light beam. It is noted that the term“chief ray” as defined herein does not necessarily propagate through acenter of an optical system.

Referring for a non-limiting illustrative example to FIG. 6A, a displayapparatus 650A, shown in a partial view, includes a self-lit displaypanel 600A optically coupled to a collimator 630. The self-lit displaypanel 600A includes an array of pixels defined by respective pixelelectrodes, as described above with reference to the self-lit displays100, 200, 300, 400 of FIGS. 1A, 2, 3, and 4 , respectively. Each pixelemits a light cone to be collimated by the common collimator 630 into acollimated light beam. The collimator 630 is disposed one focal lengthaway from the self-lit display panel 600A. In other words, the self-litdisplay panel 600A is disposed in a focal plane 632 of the collimator630. The angle of a collimated beam w.r.t. X-axis depends on thex-coordinate of the emitting pixel. For example, a pixel 601A of theself-lit display panel 600A emits a light cone, or a diverging lightbeam 602A which is collimated by the collimator 630 into a collimatedbeam 604A at an angle β w.r.t. X-axis.

Each pixel of the self-lit display panel 600A emits a light cone with achief ray perpendicular to the plane of the self-lit display panel 600Aor XY-plane, i.e. with an angle α between the chief ray and the XY planeequal to 90 degrees. In other words, most light energy emitted by thepixels propagates along Z-axis as indicated with dashed lines 606. Onecan see that outer rays (two outer rays on each side of the collimator630) get clipped and do not propagate through the collimator 630 becausein this example, the collimator 630 is smaller than the self-lit displaypanel 600A. This will result in vignetting of the image displayed by theself-lit display panel 600A.

Turning now to FIG. 6B, a display apparatus 650B includes a self-litdisplay panel 600B optically coupled to the collimator 630. The self-litdisplay panel 600B includes an array of pixels defined by respectivepixel electrodes, as described above with reference to the self-litdisplays 100, 200, 300, 400 of FIGS. 1A, 2, 3, and 4 , respectively.Each pixel emits a light cone to be collimated by the common collimator630 disposed one focal length away from the self-lit display panel 600B.The angle of the collimated beam w.r.t. X-axis depends on thex-coordinate of the pixel. For example, a pixel 601B of the self-litdisplay panel 600B emits a light cone, or a diverging light beam 602Bwhich is collimated by the collimator 630 into a collimated beam 604B atthe angle β w.r.t. X-axis. The chief ray angle of the diverging lightbeams emitted by different pixels of the self-lit display panel 600Bdepend on X-coordinate, to direct the chief rays towards the collimator630. For example, the diverging light beam 602B is tilted and notstraight as in FIG. 6A. This enables one to avoid, or significantlyreduce, the vignetting of the image displayed by the self-lit displaypanel 600B. It is further noted that the angle β of the collimated beam604B does not, in a first approximation, get impacted by the tiltingangle α of the chief ray because the angle β only depends on the pixelcoordinate. The desired directing of chief rays of the light beamsemitted by the pixels of the self-lit display panel 600B may be achievedby configuring the array of out-couplers 111 (FIGS. 1A, 2, 3, and 4 )coupled to the array of waveguides 109 for out-coupling the portions110A of the illuminating light 110 through the array of pixel electrodes107 at a chief ray angle spatially varying from one pixel electrode 107to another, e.g. to pass all rays through the collimator. It is furthernoted that the out-couplers 111 may also be configured to control thecone angle of the diverging light beams 602B of the out-coupledilluminating light portions, i.e. the angular width of the emitted lightcone 602B.

Non-limiting examples of the out-couplers 111 for any of the self-litdisplay panels of this disclosure will now be presented. Theconfigurations may be used for chief ray engineering, and may beoptimized for uniform illumination, exit pupil control, etc. Referringfirst to FIG. 7A, an out-coupler 711A includes a grating structure 702Aetched in a core 704 of a ridge-type waveguide of the PIC layer. Aperiod or pitch of the grating structure 702A may be selected toout-couple portions of the illuminating light towards the electroactivelayer at a desired out-coupling angle. The etching depth of the gratingstructure 702A may be spatially varied to provide a spatially varyingout-coupling efficiency.

In FIG. 7B, an out-coupler 711B includes a grating structure 702Bsupported by a spacer layer 706 supported by the core 704 of theridge-type waveguide. A period or pitch of the grating structure 702Bmay be selected to out-couple portions of the illuminating light towardsthe electroactive layer at a desired out-coupling angle. A thickness ofthe spacer layer 706 may be spatially varied to provide a spatiallyvarying out-coupling efficiency.

Referring now to FIG. 7C, an out-coupler 711C is similar to theout-coupler 711A of FIG. 7A. The out-coupler 711C of FIG. 7C includes aslanted grating structure 702C etched in the core 704 of a ridge-typewaveguide of the PIC layer. Slanting of the grating structure 702Cenables one to change (increase or decrease) the amount of light energygoing into a selected diffraction order.

Turning to FIG. 7D, an out-coupler 711D is similar to the out-coupler711C of FIG. 7C. The out-coupler 711D of FIG. 7D includes a binaryslanted grating structure 702D etched in the core 704 of a ridge-typewaveguide of the PIC layer. The binary slanted grating structure 702Dmay be obtained by a sequence of straight etching steps. In FIGS. 7A to7D, the grating structures 702A-702D may be provided on top and/orbottom of the respective ridge waveguides. The pitches of the gratingstructures 702A-702D may be chirped to control the cone angle, i.e. theangular spread of the out-coupled illuminating light portions.

Referring now to FIG. 8A, an out-coupler 811A is similar to theout-coupler 711A of FIG. 7A, and includes similar elements. A gratingstructure 802A etched in a core 804 of a ridge-type waveguide of the PIClayer is slanted in the plane of the PIC layer, i.e. in XY plane, toredirect the chief ray of the corresponding out-coupled illuminatinglight portion in a direction perpendicular to the core 804, e.g. towardsa collimator to reduce vignetting and to improve light utilizationefficiency as has been explained above with reference to FIGS. 6A and6B. More generally, the etched grating structure may be slanted in twoplanes, i.e. in plane of FIG. 7C (XZ plane) which is perpendicular tothe PIC layer plane (XY plane), and in plane of FIG. 8A (XY plane), toredirect the chief ray in two orthogonal directions. The etched gratingstructure 802A may also be chirped for cone angle control.

Referring to FIG. 8B, an out-coupler 811B includes a grating 802B etchedin the ridge-type waveguide 804, an optional spacer layer 806 supportedby the grating 802B, and an array of nanostructures 808 supported by thespacer layer 806. The array of nanostructures 808 may be configured toprovide the required chief ray angle, the light cone width, etc.

Turning to FIG. 8C, an out-coupler 811C includes a nanoantenna 802Cshaped and sized to provide a required angular cone width and chief rayangle of an illuminating light portion out-coupled from the core 804 ofthe ridge-type waveguide. Length L and width W of the nanoantenna 802C,and the material of the nanoantenna 802B may be selected to provide therequired out-coupling strength and angular characteristics e.g. due toelectromagnetic resonance of the nanoantenna 802C defined by itsgeometry and material. The nanoantenna 802B can be dielectric ormetallic (plasmonic). The length L and width W are typically less thanone micrometer. An array of the nanoantennae 802C may be provided, withrows of the array coupled to individual ridge waveguides. Furthermore,in all examples of the out-couplers of FIGS. 7A to 7D and 8A to 8C, therelevant parameters of the out-couplers may be spatially varied toprovide the spatially varying chief ray angle as was explained abovewith reference to FIGS. 6A and 6B.

Exemplary color illumination configurations for PIC layers in self-litdisplay panels of this disclosure will now be described. FIG. 9A is atop view of a PIC layer 908A, which is a variant of the PIC layer 108 ofany of the self-lit display panels 100, 200, 300, and 400 of FIGS. 1A,2, 3, and 4 , respectively. The PIC layer 908A of FIG. 9A includes anarray of waveguides 905A including a plurality of sub-arrays, eachsub-array being configured to carry a particular color channel of aplurality of color channels of illuminating light. Specifically in thisexample, the array of waveguides 905A includes a red waveguide sub-array904R for conveying illuminating light of a red color channel, a greenwaveguide sub-array 904G for conveying illuminating light of a greencolor channel, and a blue waveguide sub-array 904B for conveyingilluminating light of a blue color channel. The red 904R, green 904G,and blue 904B sub-arrays are interleaved and run parallel to one anotherin a common plane (i.e. XY plane), as shown in FIG. 9A. Waveguides ofthe red waveguide sub-array 904R include a plurality of gratingout-couplers 902R for out-coupling portions of the illuminating light;waveguides of the green waveguide sub-array 904G include a plurality ofgrating out-couplers 902G for out-coupling portions of greenilluminating light; and waveguides of the blue waveguide sub-array 904Binclude a plurality of grating out-couplers 902B for out-couplingportions of the blue illuminating light.

Referring to FIG. 9B, a PIC layer 908B is a variant of the PIC layer 108of any of the self-lit display panels 100, 200, 300, and 400 of FIGS.1A, 2, 3, and 4 , respectively. The PIC layer 908B of FIG. 9B includesan array of waveguides 905B having a plurality of sub-arrays, eachsub-array being configured to carry a particular color channel of aplurality of color channels of illuminating light. Specifically in thisexample, the array of waveguides 905B includes a red waveguide sub-array904R for conveying illuminating light of a red color channel, a greenwaveguide sub-array 904G for conveying illuminating light of a greencolor channel, and a blue waveguide sub-array 904B for conveyingilluminating light of a blue color channel. Waveguides of the red 904R,green 904G, and blue 904B sub-arrays run one under another at differentz-depths in the PIC layer 908B, as shown. Waveguides of the 904R, green904G, and blue 904B sub-arrays include a plurality of gratingout-couplers 902R, 902G, and 902B for out-coupling portions of red 910R,green 910G, and blue 910B illuminating light, respectively. The gratingout-couplers 902R, 902G, and 902B illuminating a same pixel are disposedone under another, as shown.

Turning to FIG. 9C, a PIC layer 908C is a variant of the PIC layer 108of any of the self-lit display panels 100, 200, 300, and 400 of FIGS.1A, 2, 3, and 4 , respectively. The PIC layer 908C of FIG. 9C includesan array of waveguides 905C, each waveguide 905C including an array ofcolor non-selective out-couplers 902. Each color non-selectiveout-coupler 902 is configured to out-couple each color channel of theplurality of color channels (i.e. the red 910R, green 910G, and blue910B illuminating light) at a substantially same chief ray angle.Examples of color non-selective out-couplers are given e.g. in U.S. Pat.No. 10,877,214 B2 to Shipton et al., which is incorporated herein byreference in its entirety.

Referring to FIG. 10 , a PIC layer 1008 is a variant of the PIC layer108 of any of the self-lit display panels 100, 200, 300, and 400 ofFIGS. 1A, 2, 3, and 4 , respectively. The PIC layer 1008 of FIG. 10comprises an array of waveguides including a plurality of sub-arrays1004-1, 1004-2, . . . , 1004-N, each sub-array coupled to a beamsplitter1009-1, 1009-2, . . . , 1009-N for illuminating a particular geometricalarea of the array of pixel electrodes 1007. Each sub-array may includered, green, and blue waveguides (i.e. waveguides configured for guidingred (R), green (G), and blue (B) illuminating light) for guiding lightof individual color channels. Such a configuration provides a self-litdisplay panel with a possibility of zonal illumination, i.e. with apossibility of reducing or even switching off illuminating light underdark areas of the image being displayed, thus achieving overall energysavings for images where only a portion of the image is bright, andimproving overall perceived image contrast.

In some embodiments, each zone is illuminated by a dedicated lasersource or a set of laser sources, or more generally semiconductor lightsources, as illustrated in FIG. 10. In some embodiments, a single lightsource per color channel may be used, e.g. a light source for R colorchannel, a light source for G color channel, and a light source for Bcolor channel. The light source of each of R, G, and B color channel maybe coupled to dedicated on-chip active PIC element(s) such as opticalswitches or variable optical splitters for example, that redistributelight energy between different zones depending on the image content.

Referring to FIG. 11 , a virtual reality (VR) near-eye display 1100includes a frame 1101 supporting, for each eye: a self-lit display panel1110 such as any of the self-lit display panels disclosed herein; and anocular lens or collimator 1120 for converting the image in linear domaingenerated by the display panel 1110 into an image in angular domain fordirect observation at an eyebox 1112. A plurality of eyebox illuminators1106, shown as black dots, may be placed around the display panel 1110on a surface that faces the eyebox 1112. An eye-tracking camera 1104 maybe provided for each eyebox 1112.

The purpose of the eye-tracking cameras 1104 is to determine positionand/or orientation of both eyes of the user. The eyebox illuminators1106 illuminate the eyes at the corresponding eyeboxes 1112, allowingthe eye-tracking cameras 1104 to obtain the images of the eyes, as wellas to provide reference reflections i.e. glints. The glints may functionas reference points in the captured eye image, facilitating the eyegazing direction determination by determining position of the eye pupilimages relative to the glints images. To avoid distracting the user withthe light of the eyebox illuminators 1106, the latter may be made toemit light invisible to the user. For example, infrared light may beused to illuminate the eyeboxes 1112.

Turning to FIG. 12 , an HMD 1200 is an example of an AR/VR wearabledisplay system which encloses the user's face, for a greater degree ofimmersion into the AR/VR environment. The HMD 1200 may generate theentirely virtual 3D imagery. The HMD 1200 may include a front body 1202and a band 1204 that can be secured around the user's head. The frontbody 1202 is configured for placement in front of eyes of a user in areliable and comfortable manner. A display system 1280 may be disposedin the front body 1202 for presenting AR/VR imagery to the user. Thedisplay system 1280 may include any of the self-lit display panelsdisclosed herein. Sides 1206 of the front body 1202 may be opaque ortransparent.

In some embodiments, the front body 1202 includes locators 1208 and aninertial measurement unit (IMU) 1210 for tracking acceleration of theHMD 1200, and position sensors 1212 for tracking position of the HMD1200. The IMU 1210 is an electronic device that generates dataindicating a position of the HMD 1200 based on measurement signalsreceived from one or more of position sensors 1212, which generate oneor more measurement signals in response to motion of the HMD 1200.Examples of position sensors 1212 include: one or more accelerometers,one or more gyroscopes, one or more magnetometers, another suitable typeof sensor that detects motion, a type of sensor used for errorcorrection of the IMU 1210, or some combination thereof. The positionsensors 1212 may be located external to the IMU 1210, internal to theIMU 1210, or some combination thereof.

The locators 1208 are traced by an external imaging device of a virtualreality system, such that the virtual reality system can track thelocation and orientation of the entire HMD 1200. Information generatedby the IMU 1210 and the position sensors 1212 may be compared with theposition and orientation obtained by tracking the locators 1208, forimproved tracking accuracy of position and orientation of the HMD 1200.Accurate position and orientation is important for presentingappropriate virtual scenery to the user as the latter moves and turns in3D space.

The HMD 1200 may further include a depth camera assembly (DCA) 1211,which captures data describing depth information of a local areasurrounding some or all of the HMD 1200. The depth information may becompared with the information from the IMU 1210, for better accuracy ofdetermination of position and orientation of the HMD 1200 in 3D space.

The HMD 1200 may further include an eye tracking system 1214 fordetermining orientation and position of user's eyes in real time. Theobtained position and orientation of the eyes also allows the HMD 1200to determine the gaze direction of the user and to adjust the imagegenerated by the display system 1280 accordingly. The determined gazedirection and vergence angle may be used to adjust the display system1280 to reduce the vergence-accommodation conflict. The direction andvergence may also be used for displays' exit pupil steering as disclosedherein. Furthermore, the determined vergence and gaze angles may be usedfor interaction with the user, highlighting objects, bringing objects tothe foreground, creating additional objects or pointers, etc. An audiosystem may also be provided including e.g. a set of small speakers builtinto the front body 1202.

Embodiments of the present disclosure may include, or be implemented inconjunction with, an artificial reality system. An artificial realitysystem adjusts sensory information about outside world obtained throughthe senses such as visual information, audio, touch (somatosensation)information, acceleration, balance, etc., in some manner beforepresentation to a user. By way of non-limiting examples, artificialreality may include virtual reality (VR), augmented reality (AR), mixedreality (MR), hybrid reality, or some combination and/or derivativesthereof. Artificial reality content may include entirely generatedcontent or generated content combined with captured (e.g., real-world)content. The artificial reality content may include video, audio,somatic or haptic feedback, or some combination thereof. Any of thiscontent may be presented in a single channel or in multiple channels,such as in a stereo video that produces a three-dimensional effect tothe viewer. Furthermore, in some embodiments, artificial reality mayalso be associated with applications, products, accessories, services,or some combination thereof, that are used to, for example, createcontent in artificial reality and/or are otherwise used in (e.g.,perform activities in) artificial reality. The artificial reality systemthat provides the artificial reality content may be implemented onvarious platforms, including a wearable display such as an HMD connectedto a host computer system, a standalone HMD, a near-eye display having aform factor of eyeglasses, a mobile device or computing system, or anyother hardware platform capable of providing artificial reality contentto one or more viewers.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments andmodifications, in addition to those described herein, will be apparentto those of ordinary skill in the art from the foregoing description andaccompanying drawings. Thus, such other embodiments and modificationsare intended to fall within the scope of the present disclosure.Further, although the present disclosure has been described herein inthe context of a particular implementation in a particular environmentfor a particular purpose, those of ordinary skill in the art willrecognize that its usefulness is not limited thereto and that thepresent disclosure may be beneficially implemented in any number ofenvironments for any number of purposes. Accordingly, the claims setforth below should be construed in view of the full breadth and spiritof the present disclosure as described herein.

What is claimed is:
 1. A method of manufacturing a self-lit displaypanel, the method comprising: forming an electronic circuitry layer on asacrificial substrate, the electronic circuitry layer comprising apixelated electrode layer comprising an array of pixel electrodes;bonding a first substrate to the electronic circuitry layer; removingthe sacrificial substrate; providing a photonic integrated circuit (PIC)layer comprising an array of waveguides for guiding illuminating lightand an array of out-couplers coupled to the array of waveguides forout-coupling portions of the illuminating light; and forming a cell byproviding a second substrate in a fixed-apart relationship with thefirst substrate, wherein the pixelated electrode layer faces the cellsuch that in operation, the illuminating light portions propagatethrough the array of pixel electrodes.
 2. The method of claim 1, whereinthe PIC layer is formed on the first substrate and faces the cell whenthe cell is formed.
 3. The method of claim 1, further comprising fillingthe cell with an electro-active material.
 4. The method of claim 3,wherein the electro-active material comprises liquid crystals.
 5. Themethod of claim 3, wherein the electronic circuitry layer is disposedbetween the PIC layer and the electro-active material.
 6. The method ofclaim 1, wherein the PIC layer is formed on the second substrate andfaces the cell when the cell is formed.
 7. The method of claim 1,further comprising forming a backplane electrode layer on the secondsubstrate before the cell is formed.
 8. The method of claim 1, furthercomprising etching away opaque material from under the pixel electrodesafter removing the sacrificial substrate.
 9. The method of claim 8,further comprising planarizing the electronic circuitry layer afteretching away the away opaque material.
 10. The method of claim 1,wherein forming the PIC layer comprises forming an array of gratings inthe array of waveguides to operate as the array of out-couplers.
 11. Themethod of claim 1, wherein forming the PIC layer comprises forming anarray of nanostructures to provide a chief ray angle of the portions ofthe illuminating light spatially varying from one pixel electrode toanother.
 12. A method of manufacturing a self-lit display panel, themethod comprising: forming a photonic integrated circuit (PIC) layercomprising an array of waveguides for guiding illuminating light and anarray of out-couplers coupled to the array of waveguides forout-coupling portions of the illuminating light; forming an electroniccircuitry layer comprising a pixelated electrode layer comprising anarray of pixel electrodes; and disposing the PIC layer relative to theelectronic circuitry layer such that in operation, the illuminatinglight portions propagate through the array of pixel electrodes.
 13. Themethod of claim 12, wherein the PIC layer is disposed on a firstsubstrate, and the electronic circuitry layer is disposed on the PIClayer.
 14. The method of claim 12, wherein the electronic circuitrylayer is disposed on a first substrate, and the PIC layer is disposed onthe electronic circuitry layer.
 15. The method of claim 12, wherein thePIC and electronic circuitry layers are disposed on first and secondsubstrates respectively.
 16. The method of claim 15, further comprisingforming a cell by disposing the first and second substrates in afixed-apart relationship with one another.
 17. The method of claim 16,further comprising filling the cell with an electro-active material. 18.The method of claim 12, wherein the PIC and electronic circuitry layersare disposed on a same substrate on top of one another.
 19. The methodof claim 18, further comprising forming a cell by providing a secondsubstrate and disposing the first and second substrates in a fixed-apartrelationship with one another.
 20. The method of claim 19, furthercomprising filling the cell with an electro-active material.